The invention relates generally to plasma processing systems, and more particularly to magnetic clips and substrate holders for use with a plasma processing system.
Plasma treatment is often used to modify the surface properties of substrates used in diverse applications relating to integrated circuits, electronic packages, and printed circuit boards. In particular, plasma treatment may be used in electronics packaging, for example, to etch resin, remove drill smear, increase surface activation and/or surface cleanliness for eliminating delamination and bond failures, improving wire bond strength, ensuring void free underfilling of chips on circuit boards, removing oxides, enhancing die attach, and improving adhesion for die encapsulation.
Typically, one or more substrates are placed in a plasma treatment system and a surface of each substrate is exposed to generated plasma species. The outermost surface layers of atoms are removed by physical sputtering, chemically-assisted sputtering, and chemical reactions promoted by the plasma. The physical or chemical action may be used to condition the surface to improve properties such as adhesion, to selectively remove an extraneous surface layer, or to clean undesired contaminants from the substrate's surface.
Conventional batch plasma treatment systems exist in which both sides of multiple large panels of material are plasma treated. Each of the panels is held by a substrate holder with a vertical orientation between a pair of planar vertical electrodes, which are energized with a suitable atmosphere present in the treatment chamber of the treatment system to generate a plasma. In such plasma treatment systems, conventional substrate holders well-suited for holding one or more substrates between the planar electrodes may be unable to effectively support thin printed circuit board material. These thin substrates, which are not rigid enough to be self-supporting, can move relative to the rack and may potentially short to one of the adjacent electrodes because of the inability of conventional substrate holders to lend rigid support to these sheets of flexible material. When a thin substrate shorts or touches an electrode, the substrate may be delaminated or otherwise damaged.
There is thus a need for a substrate holder that can rigidly support one or more thin panels or substrates during a plasma treatment process and allow the panels or substrates to be simultaneously treated on both sides at the same time.